Electric furnace.



J. L. DIXON.

ELECTRIC FUHNACE.

APPLICATION mio rEe.23.1s\5.

1 ,24 1 ,35 1. Patented Sept 25, 1917.

4 SHEETS-SHEET 2.

A TTOHNEYS JOSEPH L. DIXON, OF SHEFFIELI), ENGLAND.

ELECTRIC FURNACE.

Specification of Letters Patent.

Patented Sept. 25, 1917.

Application tiled February 23, 1915. Serial No. 9,782.

T 0 all 'whom it may concern.-

Be it known that I, Josnrn L. Dixon, a subject of the King of GreatBritain, resid ing at 6 Ashgate road, in the county ot York and cityvofSheliield, England, have' invented certain new and useful -Improvementsin Electric Furnaces; and I do hereby declare the ollowing'to be a full,clear, and exact description of the invention, such as will enableothers skilled in the art to which it a pertains to make and use thesame.

lectrie are smelting'furnaces as known heretoforecan be classified undertwo heads.

' 'First those wherein the current passes from one electrode to the'other, and second those in which substantially the entire current passesthrough the bath of metal, through the lining and back tothe generator.

Certain distinct advantages and accompanying disadvantages accompany theuse of either mode of using the current alonc and, where dierentconditions are to be 'foreseen and4 provided for, a distinct imin .thefurnace.-

provement will follow the devising of a suitable system wherein the twomodes of using the current are made optionally available in combinationor separately. Such an improvement follows from the use of my presentinvention.

The object of my invention is the construction of-fnrnaces in which theproportion of current passing through the bathV and lining is separatelycontrollable, so that if desiro'll'there can -be caused to flow throught e'bath and lining much smaller proportions of with furnaces o tioned.

I carry out my invention by several methods, the method selected in anyparticular case beingr dependent partly on the sii/.e of the "furnaces,and partly on the nature of, the metallurgical o eration to he conductedA l-the methods are'such that the power may be taken from a stnudardpoly hase supply system, n most, important euturc being that thecarrying out of the invention does not necessitate any unequal loadingof the supplysystcm.

In the accompanying drawings, Fiure l isa diagram lillustrativeof thcgeneral-princilple of my il the second type above meninvention, Fig. 21s a diagram ustrutive of the general ease wherein threepl'msecnrrentsnre applied to furnaces having an even number of upperelectrodes, Fig. 3 is a diagram showing one form of fury current thanare possblenace embodying my invention, Figs. 4 and 5 are vectordiagrams illustrative of the different conditions available in thesystem shown in Fig. 3, Fig.` 6 is a diagram illustratinv a modified'form of my invention, Figs. 8 and 9 are vector diagrams illus-l .rat-ingthe modes of use of said modification, and'Fig. 10 is a diagramillustrating still another modification;

In Fig. l, Ihave shown a furnace wherein three upper electrodes AB andCare connected to asuitable source".of threev hase current from pointsa, b and c whose p ases are 120 degrees apart, while the lower terminalN is connected to the neutral point'n.

This arrangement is within my invention `and admits of obtaining theadvantages hereinafter pointed out. l

One method of carryivri' out my invention is shown in Fi 2, in' ich F,is'the furnace, A A, B, are four electrodes (herein'nitcr termed uppcrelectrodes) which arc on to the bath of metal or alloy or othermaterial. N, is an electrode embedded in the furnace lining (hereinaftertermed a lower electrode);

The furnace is fed with two-phase seco'mlary current taken from" twosingle phase transformers, represented in' the as a., and 7), whoseprimaries are fed from three-phase mains, 1, 2nnd 3.

The two secondary terminals of thetransformer, a, are connected, one tothe electrode A1., and the other to the electrode AH The middle point ofthe secondary wind-- ing of the'transformer, a, is connected to thelower electrode N.

Similarly, the secondary terminals of the transformer, 'li are mnncctcdto the electrodes B and liz and the middle point connected to the lowerelectrode N, as shown in the diagram. v

It is apparent thaf u'hcn'tlle two electrodes A' and A?. urnsupplyiug tothe furnace currents of equal magnitude, these currents will exactlyneutralize cach other and the transformer. a, wilt supply no current tothe lou'vr rlcrlrude N. The rllltrodls, A und A2 may he adjusted so thatth'e currents in lhcm are not equal,l und therefore there is a currentflowing along the wire connected to the middle point of the transfo.mer, "a, and through the lower electrode N. To take an extreme rase forthe salio nl' illustration,

drawings the electrode A2. may he raised so that it whole of the currentin the electrode A, passes through the hath and returns to the middleVpoint of thc transformer, a. The same adJustment may he iliade with theelectrodes B1, and B2, fed by the trahsloriner, b.

Whatever adjustment is made with the four upper electrodes and whateverthe amount of current flowing through the lower electrode, theelectrical system will not be unequally loaded if the transformers a,and b, are supplying equal amounts of power to the furnace.

It is apparent that the invention may be carried out with the middlepoint of only one of the transformers connected to the lower electrode,N. l

My invention contemplates means for easily altering the connectionsbetween the transformer )rimaries and the mains l, 2 and 3 where y thephase relations in the secondaries may be so altered as to control at'will the amount of current passing through the bath to the lowerelectrode.

In Fig. 3 is shown an arrangement for this urpose wherein is used anumber of trans ormers less than the number of upper electrodes in thefurnace. In this case six upper electrodes are supplied from Afourtransformers. For this purpose two electrodes A, B are connected withthe terminals of one secondary a. Two others, C, D, are connected incommon to one secondary terminalj of b, while E and F are connected withthe outer terminals of the secondaries of qand d. 'lhe interior orcontiguous secondary terminals of c and lare connected in common withthe secondary of The four primaries of the four transformers areScott-connected with the mains 1, 2 and 3, and these connections aremade by means of multiple switches Irland Z.

W hen the switch 'is closed and switch l is open, the phaserelations-,are indicated by the diagram inlgl, ai. When Z is closed andl: is open the phase relations are those indicated in Fig.

ln Fig. (i is shown another mode of sup,- plying six electrodes froml'our transformers l'ed from the three-phase mains l, il and,

2l. llore the multiple switches l', I, m and u cause various changes inphase relations, thus; alteringr the proportion ol current going throughthe bath.

l'Vitli switchesl and m closed and switches 5,5"Z and u open,thecurreuts occupy the positions shown in the fliagrani Fig. T. and the`only current flowing through the lower elec- .lrode`is' that duo to thelill'erence in the seclondary \'oltages.

FlfVhcn larger currents "through the lowel`L` electrodes are required,the switches It' and n, are open and the s\vitcln\.s','a1id m closed,and the transformer e', supplies current `in` a reversed manner, thepositions of,. the` six currents heilig shown in Fig. 8. Similarly byopening the switches, Z and m, and closing' [he switches Il: and n, thetransformer, c will supply current 1n a reversed manner.

When still larger currents through the lower electrode are required, theswitches, I.: and m, are opened and the switches l and n, closed, andthen both the transformers c' and 0, are reversed, the secondarycurrents occupying the positions shown in Fig. 7.

W hatercr the magnitudes and positions of the secoiulary currents, theelectrical s stem will not be unequally loaded provide each of thetransformers, a, and b, is supplying power equal to the total powersupplied by the two transformers, o* and c.

In Fig, 6, I have shown the primary side ot' the transformers connectedto the supply mains in star fashion. It is apparent that withoutinterfering with the can-yin ont ot' the invention they can be connectedin delta fashion.

In all lhe methods I have described of carrying out my invention, thereis only one lower electrode embedded in the lining or sole of thefurnace. At the same time, I

wish it to be understood that my invention,

ofthe t 'ausformeis a, b, c and d. The two lower electrodes are shown atN and N and are connected rcs ectively to common secondary terminals oi)a and c, and of b and d.

lVhat I claim isl. An electric furnace having suitable u saidtransformers, a common connection between the terminals of two of saidsecondaries and the lower electrode, and suitable connections betweenthe secondaries of saidtransformers and said upper electrodes.

2. An electric furnace having suitable u per electrodes and a lowerelectrode, mam

leads for supplying three-phase alternating current, transformers lessn1 number than `said upper electrodes and so connected with said 4mainleads as to deliver two phase current from their Secundarios, switchessnit-` ably connected with the primary circuits for producingalterations iu phase relations in said transformers, and suitableconnections between Asaiil eleclrodes and the--secondaries of saidt'ahsforiners. f

3. Pili electric furnace ,haringsix upper'A electrodes and a lowerelectrode two pairs connection between the remaining second- 1u oftransformers, means for suppying alterar terminals and seid lowerelectrode. nating current to the rimaries thereof, conn testimonwhereof, I aix my signature, duotors connectn t e outer terminals of inpresence o two witnesses.

5 one pair of transfrmer secondaries each to two of the upperelectrodes, conductors con- JOSEPH L. DIXON. nectin one secondaryterminal of each of Witnesses:

the ot er transformers with one of the re- KATHARINE C. MEAD,

maining upper electrodes, and a .common GEO. A. BYRNE.

